Oscillograph sweep circuit



Patented m so, 1944 2,350,069 I OSCILLQGBAPH SWEEP Harold]; Schrader,liaddonileld, and Ronald D. Scheldorl, Haddon Heights, N. J., authors ofAmerica, a corporation 'to Radio Oormration of Delaware ApplicationFebruary 20, 1942, Serial No. 431,826

14 Claims. 1 (on. 1-11-95) This invention relates generally to cathoderay oscillo'graphs and particularly to sweep circuits for cathode rayoscillographs in which a source of electric phenomena to be observed iscaused to produce instantaneously a single timing voltage to provide asingle traversal of the fluorescent screen by the cathode ray.

More particularly, the invention relates to a circuit and method forproducing such a .single timing voltage substantially instantaneouslywith the application of the initial portion of the electric phenomena tobeobserved, and or duration and rate dependent on the time constant 01'the circuit.

Other methods and circuits for producing single timing pulses have beenused heretofore, but they have been characterized generally byconsiderable time delay between the application of the startingpotential and the beginning of the timing pulse.

This invention therefore has great utility over other systems when themeasurement of signals of short duration or transients is required. Inall such systems the transient is often used to start the timing pulse.It is obvious that any time delay between the start of the transient andthe start oi the timing pulse, both measured at the oscillograph. wouldprevent any useful indication of the transient during this interval.

Another problem innmeasuring transient voltages is caused by theircustomarily short duration. This necessitates an extremely rapidtraversal oi the screen by the cathode ray with necessarily a low amountof light energy available to the observer, resulting in poor visibility,because the cathode ray intensity must be limited during absence ofscanning signal to prevent burning of the fluorescent screen. Thisinvention provides means for increasing the intensity of the cathode rayonly during the time interval of the single timing pulse which is inturn under control ofthe transient voltage under measurement. Thisarrangement permits greatly increased illumination of the fluorescentscreen during the scanning interval and at the same time permits lownormal cathode ray intensity to prevent burning of the screen.

An object of the invention is to provide means for producing a singletiming pulse for cathode rayoscillograph seaming which is started inresponse to an initial portion of the signal under measurement and theduration or rate of which is controlled by the time constant of anassociated circuit.

Another object of. the invention is to provide a circuit or method forproducing a single timing.

pulse for use in cathode ray oscillograph measurements oLtransients, inwhich the beginning of thetransi tsubstantiallyinstantlystartsthe timingpulseand at the same time causes an increase in the intensity of thecathode ray for the duration of the timing pulse.

Still another object is to provide means for producing a singlenon-oscillatory timing pulse for osciilograph use. in response to aninitial portion of a starting signal or a transient ot a selectedpolarity wherein the rate or duration of the pulse is determined by thetime constant of the pulse circuit. An additional object is to providemanual switching means for reconditioning the circuit after eachactuation by the starting potential.

In describing the invention, reference will be made to the drawing,which shows a schematic diagram of one embodiment of the system.

Referring to the drawing, the wave form shown at the extreme left isthat of a typical transient or starting signal under measurement. Thissignal is applied to the vertical deflecting element H of theconventional oscillograph l2 and to the input it of wide band amplifiertube T1. The output of tube T1 is coupled in any conventional manner tothe input of the conventional phase inverter circuit containing tube T2.The singlepole double-throw throw switch S1 provides signals of eitherpolarity to the cathode of diode rectifier T: by utilizing either theinput or output of phase inverter tube T: as desired.

The anode of the diode T: establishes and applies a voltage of only onepolarity to the grid of tube T4 of the trigger circuit comprised of thetubes T4 and T5. It will be seen that the position of switch 81 controlsthe startingpolarity of the transient signal.

When a signal is applied to the input circuit of tube T1 the diode tube'1; will conduct on each negative cycle. The position of the switch S1is determined by the polarity of the input signal. The value of thevariable resistor R: varies the bias, and determines the voltage atwhich the diode T; will conduct. When sufiicient signal voltage isapplied to the diode Ts, it becomes conducting and the voltage developedacross the variable resistor R: causes trigger tube T4 to becomenon-conducting because of the resultant high negative grid bias applied.The value of resistance of Ra determines the sensitivity of the triggercircuit. When tube T4 becomes non-conducting, tube Ts becomesconducting. With tube Ts conducting, the grid potential of tube T4 ismade even more negative to maintain the cut-oil condition. This in turnincreases the bias on the diode tube '1: so that it becomesnon-conducting except for much higher signal voltage than is required tofirst actuate it. When tube Ta is conducting, the bias of the D.-C.amplifier tube- To is decreased, causing the anode current to iincrease. The increase 0! anode-cathode current in tube Te causes thevoltage across the resistor serving transient voltages, means 'forproducingin said circuit a single non-oscillatory timing voltage pulsein response to an initial portion of said transient voltages, a timeconstant circuit,

means for deriving from said time constant cir- 75 e v l 1 9 9 l- I Ill-torise,whichraises the potential or the oathcult a timing vol 1, 115, 1 'odeoithediode'tube'rr. andnianuallyoper rtedmeanstor Frictonditionin The anode potentialoi diode T1 rises,to offset 1 said circuitafter each applicati Q13, m. the riseinits cathode potential, at aratedete'rsient.volta ge.- w mined by. the time constant oi resistorRi and 53.. In aesthetic h! cscilloarili 'circuitior ob-z capacitor or in theanode circuit oi. the diode. -scrving transient voltages having. menufor pm. a

The amplitude of the pulse developed across ducinga single timingvoltage pulse in A the-capacitor or is determined by the static" to aninitial portion or said'tr'an sient'voltagg characteristic of the diodetube- Tr. Although and or duration-determined bythetimeoonstant thesubstitution of a triode, having sharp cut- 10 oithe'circuit, a triodeactuatedbysaid transient ofl characteristics, would be desirable fromthe 1 1 vo1tage,a-phase'inverter inthe output circuit-otstandpoints ofsensitivity and gain, the diode said triode,- a'diode selectively"connected 1, ,1.

has been Ioundto be preferable because of its, tween the output oieither said triode or-saidinherently sharper cut-oi! features. The di---phase inverter and the input of a polarized trlg ode circuit. ompri t e1'': n the i e d 1 sercircuit, a n. c. amplifier between the output laycircuit R1, Ci, can. ior special purposes, be or said triggercircuitandthe cathod r a m. caused to produce a train of pulses similarto the ond diode,a time constantcircuit in. the anode single pulsedescribed heretofore, by driving the circuit or said second [diode for.determining the diode with voltage pulses of square wave io'rm. rate ofsaid singletiming uiseendzmeem' f r irom aconventiohal square wavegenerator 20. impressing said timing pulse on' a deflectingeleconnected; across the resistor I ll through the I merit of saidcathode ray oscillogi'apli.v 'f switch 2!. The individual. pulses ofthetrain 4. In a cathode'ray osciilog raph, circuit for 6h.- would belimited in amplitude by the cut-of! serving transient voltages havingmeans for proq characteristics of the diode and of rate or duraducingv asingle timing voltage pulse in response tion determined by the timeconstant or the diode to an initial portion or said transient voltagesanode circuit, -,'ihe amplifier tube To is driven andordurationdetermined byt'he time constant" by th V lta developed across p itor C1.of thecircuit, a triode actuated by said transient Output'i'or use onthe horizontal deflecting elevoltage, a-phase inverter in the outputcircuit orment l4 oi'the cathode ray oscillograph I2 is said-triode,adiode selectively connected between taken between a' point I!onresistor It and the output of either said triode or said phaseinground. 7 verter and the input oi'a polarized trigger cir- A typicaltiming pulse devel ped by the circuit cuit, a D. C. amplifier betweenthe output of said. is shown at the extreme right side or the draw- 1trigger circuit and the cathode of a second .dimg. 1 It is apparent thatthe pulsestarts as soon ode, a time constant circuit in the anodecircuit as, the driving signal reaches a predetermined or said seconddiode for determining the rate or potential the polarity of which iscontrolled by said single timing pulse, means for impressing theposition or the switch S1 and the amplitude; said timing pulse on adeflecting element-oi said by the values oi the variable resistors R2and Ra. cathode ray oscillograph, and means ror'control- The pulse willthen continue to rise for an interling the intensity of the cathode rayin said oscil val determined bythe time constant or the cir- 40 lographby voltages derived from said timing cult comprised of resistor 7R1 andcapacitor C1. pulse circuit. i f after which it will remain atmaximum'potential 5 In a cathode ray 'oscillograph circuit for. ob-' Idetermined by the normalpotential across re- 7 serving transientvoltageshaving means iorpro sistor II. I a U ducing a single non-oscillatorytiming voltage In order to recondition the circuit for actuapulse in.response to'an portion of said tion by a subsequent transient orstarting sigtransient voltages and oi duration determined by I nal, areset switch S2 is connected between the g the time constant orthe Icircuit, a triode actugrid 01 trigger tube'Ts and nd; Temporary ated bysaid transient voltages, aphase inverter closing of this switch, whichis normally open. in the output circuit of saidtriode, adiode se shortsthe grid drcifl of tu e To, restores tubes lectively'connected betweenthe output or either Ta', T and To to-normalop rati n, and causes saidtriode or said phase inverter and the input the cathode trace to returnto its original posiof aIpolarized trigger circuit. a D. 0. ampliflertion. voltage for increasing the intensity or the between the output orsaid trigger circuit and cathode ray during the operation interval ofthethe cathode of a second diode,.a time constant circuit, to provideincreased illumination, is decircuit in the anode circuitotsaid second-diode rived from the anode circuit or tube T4 andapior determining therate .01 said single timing plied to the control grid. I! of theoscilloscope .12. pulse, and means tor impressing said timing Similarcontrol voltage could be obtained from pulse on adefiectin'g element ofsaid cathode ray;

other suitable points in thecircult. oscillograph'. A we claimv as ourinvention: a 6. In a cathode ray oscillogr'aplr circuit for obi 1. In acathode ray oscillograph circuit ior observing transient voltages havingmeans for pro- 'serving transient voltages, means for producing ducing asingle non-oscillatory timing voltage in said. circuit a single timingvoltage pulse in pulse in response to aninitial portion of saidtranresponse to an i tial portion of saidtransient sient voltages and ofduration determined by the voltages, a tim onstant circuit, means fordetime constant of the circuit, atriode actuated by riving from said.time constant circuita timin Said nsient voltage. Phase i v 1!! evoltage pulse for said transient, and manually output circuit of saidtriode, a, diode H selectively operable means .ior reconditioning saidcircuit connected between the output of 'either'said'tri- I after eachapplication or said transient voltages. ode or said phase inverter andthe input oi a 2, In a cathode ray oscillograph circuit for obpolarizedtrigger circuit, a D.v C. amplifier be-.

I tween the output of'said trigger circuitjand the cathode of a seconddiode, a time constant circuit, in the anode circuit of said seconddiode for de-r.

termining'th'e rate of said single timing pulse, means for impressingsaid timingjpulse on a dc;

fleeting element of said cathode ray oscillograph,

means for controlling the intensity of the cathode ray in saidoscillograph by voltages derived from said timing pulse circuit.

'7. In a circuit for producing a single pulse of predetermined duration,a source of starting potential, a polarized trigger circuit comprising adiode having a cathode and anode, a first triode having a cathode, acontrol electrode and an anode, a second triode having a cathode, acontrol electrode and an anode, a connection from the anode of saiddiode to the control electrode of said first triode, a resistor fromsaid control electrode of said first triode to the anode of said secondtriode, a resistor from the anode of said first triode to the controlelectrode of said second triode, means for providing control electrodeand anode potentials to each of said triodes, a circuit for applying thestarting potential to the cathode of said diode, means connecting thecontrol electrode of said second triode to the cathode of a seconddiode, a time delay circuit in the anode circuit of said second diode,and means for utilizing pulses developed across said second diode.

8. In a cathode ray oscillograph circuit for measuring transientvoltages, means for producing a single timing voltage pulse in responseto an initial portion of said transient voltages and of durationdetermined by the time constant of the circuit, comprising, incombination, a triode actuated by said transient voltage, a phaseinverter in the output circuit of said triode, a diode selectivelyconnected between the output of either said triode or said phaseinverterand the input of a polarized trigger circuit, a D. C. amplifierbetween the output of said trigger circuit and the cathode of a seconddiode, a time constant circuit in the anode circuit of said second diodefor determining the rate of said single timing pulse, means forimpressing said timing pulse on a deflecting element of said cathode rayoscillograph, and manually operable means for reconditioning saidcircuit after each application of said transient voltages.

9. In a cathode ray oscillograph circuit for observing transientvoltages having means for producing a single timing voltage pulse inresponse to an initial portion of said transient voltages and ofduration determined by the time constant of the circuit, a triodeactuated by said transient voltage, a phase inverter in the outputcircuit of said triode, a diode selectively connected between the outputof either said triode or said phase inverter and the input of apolarized trigger circuit, a D. C. amplifier between the output of saidtrigger circuit and the cathode of a second diode, a time constantcircuit in the anode circuit of said second diode for determining therate of said single timing pulse, means for impressing said timing pulseon a deflecting element of said cathode ray oscillograph, means forcontrolling the intensity of the cathode ray in said oscillograph byvoltages derived from said timing pulse circuit, and manuallv operablemeans for reconditioning said circuit after each application of said,

the time constant of the circuit, a triode actuated by said transientvoltage, a phase inverter in the output circuit of said triode, a diodeselectively connected between the output of either said triode or saidphase inverter and the input of a polarized trigger circuit, a D. C.amplifier between the output of said trigger circuit and the cathode ofa second diode, a time constant circuit in the anode circuit of saidsecond diode for determining the rate of said single timing pulse, meansfor impressing said timing pulse on a deflecting element of said cathoderay oscillograph, and manually operable means for reconditioning saidcircuit after each application of said transient voltages.

11. In a cathode ray oscillograph circuit for observing transientvoltages having means for producing a single non-oscillatory" timingvoltage pulse in response to an initial portion of said transientvoltages and of duration determined by the time constant of the circuit,a triode actuated by said transient voltage, a phase inverter in theoutput circuit of said triode, a diode selectively connected between theoutput of either said triode or said phase inverter and the input of apolarized trigger circuit, a D. C. amplifier between the output of saidtrigger circuit and the cathode of a second diode, a time constantcircuit in the anode circuit of said second diode for determining therate of said single timing pulse, means for impressing said timing pulseon a deflecting element of said cathode ray oscillograph, means forcontrolling the intensity of the cathode ray in said oscillograph byvoltages derived from said timing pulse circuit, and manually operablemeans for reconditioning said circuit after each application of saidtransient voltages.

12. In a circuit for producing a single pulse of predetermined duration,a source of starting po tential, means for producing said pulse inresponse to an initial portion of said starting potential and ofduration determined by the time constant of the circuit, and manuallyoperable means for reconditioning said circuit after each application ofsaid starting potential.

13. In a circuit for producing a single nonoscillatory pulse ofpredetermined duration, a source of starting potential, means forproducing said pulse in response to an initial portion of said startingpotential and of duration determined by the time constant of thecircuit, and manually operable means for reconditioning said circuitafter each application of said starting potential.

14. An oscilloscope deflection circuit for producing a single sweepdeflection potential in response to a transient phenomenon comprising anon-oscillatory control impulse generating device responsive to theinitial part of the transient phenomenon for generating a single controlimpulse, means including a time constant circuit for producing asubstantially constant rate of change of potential in a predeterminedpolarity direction in response to the generated control impulse, andmeans to reset the control impulse generating mean: and to produce achange of potential in the opposite polarity direction in order that theJ circuit may berendered responsive to the next succeeding transientphenomenon.

